src/hotspot/share/code/nmethod.cpp

rev 54589 : 8219586: CodeHeap State Analytics processes dead nmethods
Reviewed-by:

@@ -843,10 +843,28 @@
 }
 
 #undef LOG_OFFSET
 
 
+// Iterating over all nmethods, e.g. with the help of CodeCache::nmethods_do(fun) was found
+// to not be inherently safe. There is a chance that fields are seen which are not properly
+// initialized. This happens despite the fact that nmethods_do() asserts the CodeCache_lock
+// to be held.
+// To bundle knowledge about necessary checks in one place, this function was introduced.
+// It is not claimed that these checks are sufficient, but they were found to be necessary.
+bool nmethod::access_is_safe(nmethod* nm) {
+  Method* method = (nm == NULL) ? NULL : nm->method();  // nm->method() may be uninitialized, i.e. != NULL, but invalid
+  return (nm != NULL) && (method != NULL) &&
+         nm->is_alive() && !nm->is_not_installed() &&
+         os::is_readable_pointer(method) &&
+         os::is_readable_pointer(method->constMethod()) &&
+         os::is_readable_pointer(method->constants()) &&
+         (method->signature() != NULL) &&
+         os::is_readable_pointer(method->signature());
+}
+
+
 // Print out more verbose output usually for a newly created nmethod.
 void nmethod::print_on(outputStream* st, const char* msg) const {
   if (st != NULL) {
     ttyLocker ttyl;
     if (WizardMode) {